<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        #menu{
            width: 300px;
            height: 50px;
            background-color: brown;
            text-align: center;
        }
        #menu:hover #cd{
            position: relative;
            top: 0px;
        }

        span{
            color: white;
            font-size: 20px;
            /* 水平和div居中 */
            line-height: 50px;    
        }
        #cd{
            background-color: rgb(245, 115, 115);
            width: 300px;
            height: 300px;
            position: relative;
            top: -300px;
            z-index: -1;
            transition: 0.5s;
        }
        
    </style>
</head>
<body>
    <div id="menu">
        <span>abc</span>
        <div id="cd">
            <div class="itme"><span>选项1</span></div>
            <div class="itme"><span>选项2</span></div>
            <div class="itme"><span>选项3</span></div>
            <div class="itme"><span>选项4</span></div>
            <div class="itme"><span>选项5</span></div>
            <div class="itme"><span>选项6</span></div>
        </div>
    </div>
    
</body>
</html>